Japanese Patent Application Publication No. 2010-224755 has heretofore disclosed a technique to calculate the position and attitude angle of a moving body by using a particle filter. In this technique, a plurality of particles is dispersed in the vicinity of the position and attitude angle of a moving body calculated by odometry. Then, of these particles, the particle with the closest match with values measured by a laser sensor mounted to the moving body is calculated as the true values of the position and attitude angle of this moving body.
In doing so, how much the position and attitude angle calculated using the particle filter are corrected is calculated successively, and a existent distribution range within which to disperse the particles is set in accordance with the history of these amounts of correction.
Here, the above conventional technique takes into consideration an error in the advancing direction of the vehicle but does not sufficiently take into consideration an error in the vehicle width direction. In particular, when the vehicle corners at high vehicle speed, a large movement is produced on the vehicle in the vehicle width direction, thus causing a large error in the vehicle width direction. However, this situation is not sufficiently handled in the conventional practice. This leads to a problem in that the particle existent distribution range is set with a delay and therefore fails to be set appropriately.